Friday, 15 February 2013

On meteorites

It is not often that something I'm already researching becomes front page news, but yesterday's dramatic meteor storm over Russia has prompted me to post up this article.

As any textbook will tell you, initial reports of stones falling from the sky were treated as superstitious nonsense. Stones in the sky were considered an impossibility, and most of the witness reports were from ancient history or from the uneducated classes. I was interested to know more about how the theory (that these stones came from outer space) went from instant dismissal to final acceptance.

Throughout the 1700s, meteor sightings were reported in newspapers and scientific journals. However, it was not taken seriously as a field of research until 1792 when a German scientist Ernst Chladni put together a review of all the reports he could find and concluded that they had an extra-terrestrial origin.

This theory, although widely publicised, was not taken seriously. An encyclopaedia entry from 1803 writes about this new theory as if it is an amusing curiosity.

"[A] new and very singular hypothesis has been framed by Professor Chladni of Wittenberg, who maintains it by argument, which, however fanciful, are yet worthy of the reader's notice."

After a lengthy and even-handed explanation of Chladni's ideas, the author ends with a reference to the atheism that had recently spread throughout France after the Revolution.

"Whether Chladni be a philosopher of the French school we know not; but some parts of his theory tend strongly towards materialism; and the arguments by which he attempts to prop those parts are peculiarly weak. [...] but how absurd would it be to say, that the system of general laws, by which the Author and Governor of the universe connects together its various parts, and regulates all their operations, possesses, independently of him, the power to produce worlds and whole systems, to destroy them, and from their materials to form new ones!"

This section taken from an encyclopaedia published in 1810

In the years following Chladni's work, an English scientist called Edward Charles Howard managed to obtain samples from various meteorites and concluded that (a) they were all similar in composition and (b) they were all unlike any known terrestrial rock.

In 1818, A System of Chemistry summarises the current arguments:

"Chladni endeavoured to prove that the meteors from which they fell were bodies floating in space, unconnected with any planetary system, attracted by the earth in their progress, and kindled by their rapid motion through the atmosphere. But this opinion is not susceptible of any direct evidence, and can scarcely be believed, one would think, even by Dr. Chladni himself."

Meanwhile, the most supported theory for the origin of meteorites is described as:

"The greater number of philosophers consider them, [...] as concretions actually formed in the atmosphere. This opinion is undoubtedly the most probable of all; but in the present state of our knowledge, it would be absurd to attempt any explanation of the manner in which they are formed."

Interest in meteorites had meant increased observations such that by 1841 Chladni's hypothesis is described as "that which appears to have met with most favour" although the article by Rosina Zornlin lists a number of objections to Chladni's theory.

Finally, in 1864 it appears that Chladni's theory has all but won the day, as Alexander Herschel writes that "Observations of luminous meteors have now divided themselves into three classes, for each of which a separate investigation leads to the uniform result that the hypothesis of Chladni is the only one which bears upon its face the stamp of truth."

A fair amount has been written about the controversy surrounding meteorites, and I may return to this in the future. However, the claim that researching it could end a scientist's career in ridicule doesn't seem to have been the case, since Chladni went on to become even more famous for his work in acoustics.

CHLADNI, E. (1792) "Über den Ursprung der von Pallas gefundenen und anderer ihr ähnlicher Eisenmassen und über einige damit in Verbindung stehende Naturerscheinungen"
HERSCHEL, A. (1864) “The Chemical News and Journal of Physical Science”, Vol.1 (American reprint), Crookes, W. (ed.) p.286
THOMAS, T. (1818) "A System of Chemistry in Four Volumes", vol 3 p160-161
WILKES, J. (ed.) (1810) "Encyclopaedia Londinensis", vol 7, p.386
ZORNLIN, R., (1841) "The London, Edinburgh and Dublin Philosophical Magazine and Journal of Science," Brewster, D., Taylor, R., Phillips, R., Kane, R., Brayley, E.W. (eds.), vol 19, July- December 1841, p547-548

"Supplement to the Encylopaedia, or Dictionary of Arts, Sciences, and Miscellaneous Literature in three volumes", vol 2, 1803, p40-42

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